1. Office Hours changed (today only!) 11:00 am-12:30 pm EXAM #3 Results Chapter 8 Homework posted Today’s Topic: Lewis Structures November 11, 2009

2. Bond Types 1. Ionic  Metal & Nonmetal  Charged atoms- based on electrostatic attraction 2. Covalent  Nonmetal & nonmetal  Uncharged atoms- electrons are “shared”  e - - p + attractions and p + - p + or e - - e - repulsion between atoms 3. Metallic  Special type of covalent bonding for solids

3. Balance of Forces in Covalent Bonding Bond will form when the balance of forces favors bonding (attractions > repulsions)

4. Valence Electrons Te (Group 6A) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 4

5. Lewis Structures (Lewis Dot Symbols) for Atoms

6. How many valence electrons does a Sn atom have? 1. 1 2. 2 3. 3 4. 4 5. 5 6. 6 7. 7 8. 8

7. Please make your selection... 1. Choice One 2. Choice Two 3. Choice Three 4. Choice Four 5. Choice Five 6. Choice Six 7. Choice Seven 8. Choice Eight

8. Lewis Electron Dot Structures Describe Bonding in p-block Elements

9. What do those lines and dots mean? A Lewis structure for a molecule describes the arrangement of electrons  Only valence electrons used  Lines=bonds  Dots= electrons that aren’t in a bond

10. What can a Lewis Structure do for us?

11. Rules for Drawing Lewis Structures 1. Write the skeletal structure 2. Add up the total # of valence electrons 3. Draw a bond between the central atom and each surrounding atom 4. Add lone pairs to the outer atoms to complete their octets 5. Add remaining electrons to central atom 6. If central atom does not have an octet, “borrow” electrons from other atoms (make double/triple bonds)- DO NOT ADD ELECTRONS (F and Cl do not form multiple bonds; C, N, O, P, and S do) 7. Sometimes you can’t complete an octet (B and Be)